<template>
  <div>
    <router-link 
      tag="div" 
      to="/" 
      class="header-abs"
      v-show="showAbs">
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
    <div 
      class="header-fixed" 
      v-show="!showAbs"
      :style="opacityStyle">
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      景点详情
    </div>
  </div>
</template>

<script>
export default {
  name:'DetailHeader',
  data(){
    return{
      showAbs:true,
      opacityStyle:{
        opacity:0
      }
    }
  },
  methods:{
    handleScroll(){
      const top = document.documentElement.scrollTop
      if(top>60){
        let opacity=top / 140
        opacity=opacity > 1 ? 1 : opacity
        this.opacityStyle={ opacity }
        this.showAbs=false
      }else{
        this.showAbs=true
      }
    }
  },
  activated(){
    window.addEventListener('scroll',this.handleScroll)
  },
  deactivated(){
    window.removeEventListener('scroll',this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
.header-abs
  position absolute
  left .2rem
  top .2rem
  width .8rem
  height .8rem
  line-height .8rem
  border-radius .4rem
  text-align center
  background rgba(0,0,0,.8)
  .header-abs-back
    color #fff
    font-size .4rem
.header-fixed
  z-index 2
  position fixed
  top 0
  left 0
  right 0
  height $headerHeight
  line-height $headerHeight
  text-align center
  color #fff 
  background $bgColor
  font-size .32rem
  .header-fixed-back
    position absolute
    top 0
    left 0
    width .64rem
    text-align center
    font-size .4rem
    color #fff
</style>